KUZHEL, S. A. Space boundary values and correct expansions of the Hermitian operators . Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 42, n. 6, p. 854–858, 1990. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/8853. Acesso em: 6 dec. 2025.